A conventional gas turbine is caused to drop its output in a summer season when the temperature increases, therefore, various arrangements have been proposed as a method to recover the dropped output.
JP-A Laid-Open No. 7-97933, JU No. 61-37794, or JP-A Laid-Open No. 5-195809 disclose that the intake air of the compressor is cooled.
Further, JP-A Laid-Open No. 61-283723 discloses that water is supplied from the inlet of the compressor and from the intermediate stage of the compressor in a combined system of a gassification furnace and a gas turbine.
Further, JU-A No. 56-43433 discloses that a supply port through which to supply water droplets is provided in its compressor, and JP-A No. 2-211331 discloses a gas turbine which is provided with two types of compressors of a high pressure and a low pressure, and an intermediate cooler which is provided between these two types of compressors. Still further, JP-A No. 6-10702 discloses a technique to inject water into an intermediate section between an upper-stream compressor stage and a down-stream compressor stage in a compressor group having a plurality of compressor stages in order to reduce power consumption.
However, what are disclosed by these related arts of JP-A No. 7-97933, JU No. 61-37794 or JP-A No. 5-195809 are addressed simply to dropping temperatures of intake air to be admitted into the compressor so as to be able to improve its output. JP-A No. 61-283723 merely discloses vaporization of water droplets in the compressor and utilization thereof as a medium to cool the turbine blades, and as a consequence, improvement of turbine cycle characteristics.
Further, JP-A No. 2-211331 discloses the gas turbine which is provided with an intermediate cooler which is provided between the two types of compressors of high pressure and low pressure, and wherein means for detecting a temperature and a humidity at the inlet of the high pressure compressor are provided, and a feed water flow to the intermediate cooler is controlled. However, this control does not teach nor suggest water injection into the compressor itself, and is not concerned with control of humidity at the inlet of the compressor.
In consideration of an actual operation of a gas turbine or a combined cycle using a gas turbine and a steam turbine, there is required a development of a system which can realize a safety operation of the gas turbine while always ensuring protection of the gas turbine itself, and which can improve its output and thermal efficiency using a simple arrangement.